Procainamide in the Induction and Perpetuation of Ventricular Tachycardia in Man

The effects of a single intravenous infusion of 750 mg of procainamide was studied in 12 patients with symptomatic chronic recurrent ventricular tachycardia in whom ar rhythmias could reproducibl be initiated and terminated by programmed electrical stimulation of the heart. Sustained ventricular tachycardia was induced in 6 patients and non-sustained tachycardia was induced in the remaining 6 patients during control studies. Following procainamide (plasma level 10.3 ± 3.7mcg/ml), ventricular tachycardia couid be induced in 10/12 patients, sustained in 4 patients and non-sustained in the remaining 6 patients. In 8/12 patients (66%). induction of ventricular tachycardia was facilitated as demonstrated by: (1) tachycardia zone was widened in 4 patients and was un changed in another 3 patients; (2) non-sustained ventricular tachycardia was changed to sustained ventricular tachycardia in one patient. The ventricular tachycardia had a faster rate and a different QRS morphology; (3) in 4 patients tachycardia was inducible with a lesser number of extrastimuli an d/or hy spontaneously occurring ventricular premature depolarization and; (4) increase of the num ber of induced ventricular responses of non-sustained ventricular tachycardia. In 4/12 patients (33%), procainamide abolished or modified the induction of ventricular tachycardia as demonstrated by: (1) inability to induce ventricular tachycardia in 2 patients; (2) narrowing of the tachycardia zone and conversion from sustained into non-sustained ventricular tachycardia (one patient) and; (3) decrease in the number of induced ventricular responses in one patient. The response to procainamide could not be predicted from rates of spontaneous ventricular tachycardia, induced ventricular tachycardia during control studies, degree of slowing of ventricular tachycardia or from prolongation of the coupl ing interval after procainamide. These results suggest that instead of abolishing the arrhythmia, pro cainamide in frequently employed doses in patients with chronic recurrent ventricular tachycardia can facilitate its initiation sometimes at even faster rates. Patients not responsive to the usual doses of procainamide should undergo acute drug testing trials to determine the optimal dose/drug levels. (PACE, Vol. 5, May-June, 1982)